THE NERVOUS SYSTEM 



295 



Since the white matter consists of fibres and the gray of 

 cells, the conclusion is that in general the white central 

 layers of the brain are 

 made up of fibres 

 arising from the cells 

 that lie near its sur- 

 face. Every nerve 

 fibre is really a part 

 of a nerve cell, how- 

 ever far from the cell 

 it may extend. This 

 relation of the white 

 to the gray matter 

 should be kept in 

 mind during all our 

 discussion of brain 

 structure and func- 

 tion. If the cells of 

 the cerebrum were in- 

 active the heart beat 

 and breathing might 

 continue; but there 

 would be no powers of 

 sensation, of thought, 

 of judgment or of vo- 

 lition, no emotions, no 



FIG. 150. DIAGRAM 



To show the courses of fibres through thebrain. It 

 will be seen that all paths to or from the spinal 

 cord cross, those from the brain crossing at the 

 base of the brain, and those to the brain crossing 

 lower down. Outer shaded area represents the 

 cortex of the cerebrum; inner shaded areas are 

 subordinate nerve centers. (Landois) 



anticipation nor mem- 

 ory; lacking the cells 

 of the cortex one could not consciously move any muscle of 

 the body. Thus, in the cells of the gray matter of the cerebrum 

 reside all powers of sensation, of voluntary motion and what 

 we call intellect. 



One other very important fact should be mentioned here; 

 the cells in the right half of the cerebrum are, to quite an extent, 

 connected by fibres with the left side of the body, and those 



